DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 171932
SWODY1
SPC AC 171930

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 PM CDT MON SEP 17 2007

VALID 172000Z - 181200Z

..THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY TO THE
CENTRAL PLAINS...

..UPPER MS VALLEY TO CENTRAL PLAINS...

SEVERAL IMPULSES ROTATING THRU THE PROGRESSIVE WRN TROUGH. LEAD
S/WV LIFTING NNEWD THRU WRN HI PLAINS WITH UPSTREAM SYSTEM HEADING
NE ACROSS CENTRAL ROCKIES. WITH YET ANOTHER S/WV TRACKING EWD
ACROSS SRN INTERMOUNTAIN REGION STRONG FORCING WILL BE SLOW TO BEGIN
INTERACTING WITH THE MOISTURE/INSTABILITY THAT CONTINUES TO FLOW NWD
THRU THE PLAINS AHEAD OF THE COLD FRONT.

AT 18Z THE PRIMARY FRONTAL ZONE EXTENDED FROM THE CENTRAL DAKOTAS
SSWWD INTO NWRN KS AND WWD TO CENTRAL ROCKIES. ONLY MODEST LAPSE
RATES AND RELATIVELY WARM AIR AT MID LEVELS WILL DELAY ONSET OF
SURFACE BASED STORMS THRU MUCH OF THE AFTERNOON ALONG/AHEAD OF COLD
FRONT. STRONGEST HEATING IS OCCURRING CENTRAL HIGH PLAINS FROM KS
TO SRN NEB WITH MLCAPES CLIMBING TO 1500 TO 2000 J/KG BY LATER THIS
AFTERNOON.

AS OF 19Z SURFACE BASED CONVECTION WAS BEGINNING TO DEVELOP IN AREA
OF FRONTAL CONVERGENCE FROM BBW SWWD TO E OF GLD THEN TO NEAR LHX.
WHILE GREATER SURFACE INSTABILITY IS IN THIS AREA...THIS REGION IS
WELL AHEAD OF ANY UPPER SUPPORT FROM THE TROUGH TO THE W WITH
SFC-6KM SHEAR GENERALLY LESS THAN 30KT.

THUNDERSTORMS WILL DEVELOP ALONG THE FRONT CENTRAL PLAINS DURING THE
NEXT FEW HOURS AS WARM SECTOR CONTINUES TO HEAT. SEVERE THREAT IS
EXPECTED TO BE ASSOCIATED WITH PRIMARILY MULTI-CELLULAR STORMS WITH
HAIL AND DOWNBURSTS WINDS.

HEIGHT FALLS AND LARGE SCALE ASCENT WILL SPREAD EWD ACROSS HIGH
PLAINS BY THIS EVENING AS TROUGH CONTINUES ENEWD ACROSS ROCKIES.
ACCORDINGLY THE MID LEVEL CAP SHOULD WEAKEN ALONG AND AHEAD OF THE
FRONTAL BOUNDARY NEWD INTO UPPER MS VALLEY PRIMARILY AFTER 00Z.

GIVEN THAT THE STRONGEST STORM DEVELOPMENT WILL MOST LIKELY OCCUR
NOT UNTIL CLOSE TO EVENING AND SHEAR/LAPSE RATES ARE NOT
PARTICULARLY IMPRESSIVE...EXTENT OF SEVERE THREAT IS STILL SOMEWHAT
UNCERTAIN...BOTH IN LOCATION AND COVERAGE.

AFTER 00Z SHEAR DOES BECOME MORE SUPPORTIVE OF SUPERCELLS UPPER MS
VALLEY...HOWEVER INSTABILITY AND CINH WILL BE A LIMITING FACTOR.

.HALES.. 09/17/2007

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